Investigations on the relationship between malignancy and differentiation continue. Cloned tissue culture lines of Friend leukemic cells stimulated to differentiate along the erythroid line by growth in the presence of DMSO, other polar solvents and structurally unrelated inducers, such as butyric acid, hemin and hypoxanthine, are being studied. The patterns of enzymes known to be involved in hemoglobin synthesis, in purine metabolism and differentiation of erythroid cells are being explored. Attempts to demonstrate in vivo transformation with Friend leukemia virus are also in progress. BIBLIOGRAPHIC REFERENCES: Golde, D.W., A. Faille, A. Sullivan and C. Friend: Granulocytic stem cells in Friend leukemia. Cancer Res. 36:115-119, 1976. Darzynkiewicz, Z., F. Traganos, T. Sharpless, C. Friend and M.R. Melamed: Nuclear chromatin changes during erythroid differentiation of Friend virus-induced leukemic cells. Exp. Cell Res. 99:301-309, 1976.